1. Field of the Invention
The present invention relates generally to aerosol generators and, more particularly, to aerosol generators which include a heater for volatilizing liquid material. The present invention also relates to methods for generating an aerosol. The present invention has particular applicability to the generation of aerosols containing medicated material.
2. Description of the Related Art
Aerosols are gaseous suspensions of fine solid or liquid particles and are useful in a wide variety of applications. For example, medicated liquids and powders may be administered in aerosol form. Such medicated aerosols include, for example, materials which are useful in the treatment of respiratory ailments, in which case the aerosols may be inhaled into a patient""s lungs. Aerosols may also be used in non-medicinal applications including, for example, dispensing air fresheners and insecticides and delivering paints and/or lubricants.
In aerosol inhalation applications, it is typically desirable to provide an aerosol having an average mass median particle diameter of less than 2 microns to facilitate deep lung penetration. Most known aerosol generators are incapable of generating aerosols having an average mass median particle diameter less than 2 microns. Also, in certain applications, it is generally desirable to deliver medicated material at high flow rates, for example, above 1 mg per second. Most known aerosol generators suited for delivering medicated material are incapable of delivering material at such high flow rates while maintaining a suitable average mass median particle diameter. In addition, most known aerosol generators deliver an imprecise amount of aerosol compared with the amount of aerosol that is intended to be delivered.
Commonly owned U.S. Pat. Nos. 5,743,251 and 6,234,167, disclose aerosol generators designed for volatilizing a liquid and ejecting the volatilized liquid into the atmosphere. The volatilized liquid subsequently condenses, thereby forming an aerosol. Such aerosol generators may utilize resistance heating materials to volatilize the liquid. However, generators having a single zone wherein the liquid is heated may not provide optimal delivery of the volatilized liquid.
In light of the foregoing, there exists a need in the art for the provision of an aerosol generator which provides improved aerosol delivery of volatilized liquid.
According to a first aspect of the present invention, an aerosol generator includes a liquid supply, a flow passage having at least one inlet that is in fluid communication with the liquid supply, the flow passage including at least first and second flow paths and at least one outlet, and a heater arrangement including first and second heating sections, the first heating section being adapted to heat liquid in the first flow path sufficiently to vaporize the liquid so as to form a vaporized liquid ejected from the at least one outlet, and the second heating section being adapted to heat liquid in the second flow path sufficiently to vaporize liquid so as to form a vaporized liquid ejected from the at least one outlet.
The invention also provides a method for generating an aerosol using an aerosol generator comprising (1) a flow passage having an inlet in fluid communication with a liquid supply, the flow passage including at least first and second flow paths and at least one outlet; and (2) a multi-path heater arranged to volatilize fluid, wherein the heater includes at least first and second heating sections, the first heating section being adapted to heat liquid in the first flow path sufficiently to vaporize the liquid so as to form a vaporized liquid ejected from the at least one outlet, and a second heating section being adapted to heat liquid in the second flow path sufficiently to vaporize the liquid so as to form a vaporized liquid ejected from the at least one outlet, the method comprising activating the heater arrangement of the aerosol generator to provide a differential heating rate in the first and second flow passages, and directing a smaller amount of volatilized fluid out of the first flow path, prior to directing the bulk of volatilized fluid out of the second flow path.